1. Field of The Invention
This invention relates to the reeling of a wound web roll. More particularly, this invention relates to an improved method and apparatus for reeling a wound web roll which is maintained under torsion, nip pressure and web tension substantially at all times during formation. Still more particularly, this invention relates to an improved reel on a paper-making machine, and an improved method of reeling paper onto a reel spool, wherein the reel spool is continuously supported on a pair of spaced, horizontally disposed rails during the reeling process while a support drum nips, and partially supports from below, the paper web roll being wound by substantially vertical translational movement.
2. Description of The Prior Art
The reel on a paper-making machine has not changed conceptually for the past thirty or more years. Such a prior-art type of paper making machine reel is exemplified by the so-called Pope type of reel as shown and described in U.S. Pat. No. 3,743,199. The Pope-type of reel operates satisfactorily, but it and all other prior types of reels have deficiencies which become increasingly significant and harmful to paper quality as the reeling speeds increase and the desired diameters of the finished wound paper rolls become larger.
Thus, in a Pope-type of reel, the new reel spool is initially engaged by a pair of primary arms while the first few wraps of paper web are wound onto the reel spool. The newly started wound web roll is then brought into nipping engagement with a support drum while the on-coming paper web continues to be wrapped into a new wound roll. As the wound paper roll begins to increase in diameter, it is rotated by the primary arms about the periphery of the support drum and transferred onto a pair of substantially, horizontally disposed support rails. On almost all existing Pope-type reels, torque either was not, or could not, be applied to the reel spool while it was held in the primary arms. When the reel spool has been rotated down to be supported on the support rails, a pair of secondary arms then maintain the wound paper roll in nipping engagement with the support drum with the nip in a substantially horizontal plane through the rotational axis of the paper roll being wound. Torque is applied to the wound paper roll being wound generally after it has been transferred to the secondary arms.
The wound paper roll thus follows a complicated, non-smooth path from the location where the on-coming web is initially wrapped onto the new reel spool, to the point where it is brought into a nipping engagement with the support drum and is then rotated downwardly about the periphery of the support drum by the primary arms, to the point where it is supported by the support rails and is moved horizontally on the rails as its diameter builds.
This complicated path causes difficulty in that it limits the time during the wound roll building process when center-wind torque can be applied to the reel spool. To optimize wound paper roll structure, torque must be provided to the developing roll from the beginning. Mechanisms which provide torque through the primary arm rotation, such as shown and described in Patent DE 40 07 329 A 1, are complicated, costly and may do more harm than good if there is no compensation for the weight of the mechanism. Further, if torque has been applied to the reel spool while it is supported in the primary arms, the Pope-type reels require that there be a torque transfer to the reel spool of the developing roll when it is transferred from the primary arms onto the support rails and is engaged by the secondary arms to provide nip pressure against the support drum.
Thus, in prior-art reel arrangements, torque is applied either intermittently or when the wound roll is engaged by the secondary arms. Nip pressure is applied substantially by gravity while the roll is supported in the primary arms, and is supplied by hydraulically or pneumatically actuated mechanisms while the roll is supported in the secondary arms. Finally, without a highly wrapped roll, nip, or other tension isolating mechanism between the reel and upstream processes, the sheet/web tension required for good roll structure may be unattainable due to runability problems.
A further deficiency in prior reeling arrangements resides in the fact that the paper roll being wound is supported solely by its reel spool journals on the support rails during the intermediate and final stages of its formation when its diameter and weight are both increasing. Paper wound onto the new reel spool at the beginning of the reeling operation tends to burst, tear, wrinkle and exhibit other defects as the wound paper roll diameter, and pressure exerted near the core, increases and the web tension and wound roll weight increase and the reel spool deflects. This deflection also creates a non-uniform nip distribution across the face of the wound web roll. This non-uniformity creates further problems in turn-up efficiency and in paper defects. Such defects currently cause losses amounting to 1%-5% of the total production of a paper making machine.
When the initial paper web wraps on the reel spool, or core as the reel spool is sometimes called, are not tight enough, there is layer-to-layer slippage. Wound paper rolls must be structured properly, in terms of web tension at different radial distances from the reel spool, to avoid inducing web defects during the reeling operation. It is imperative that the initial paper web wraps on the reel spool/core be tight enough to avoid layer-to-layer slippage and bursting. At the same time, the wound-in-tension must not exceed the web sheets' tensile strength. Radial strains induced by each subsequent web wrap reduces the wound-in-tension of the layer beneath it. Each wrap throughout the wound web roll should be wound with slightly less tension than the previous wrap to minimize this effect. Abrupt changes in roll hardness must also be avoided to eliminate sheet defects within the roll.
It is known that the three parameters influencing wound roll hardness are 1) the torque applied to the spool/core, 2) the linear nip pressure between the wound web roll and the support drum, 3) the tension in the on-coming web being wound into the roll. Existing reels use complicated, expensive, yet sometimes ineffective, control schemes to provide nip pressure between the wound web roll and the support drum. The use of two sets of loading arms (i.e. primary and secondary arms) while moving the wound web roll through an abruptly changing path of travel as it is being wound exacerbates, if not causes, this difficulty. The abruptly changing path of wound roll travel also limits the use of center-wind torque on the reel spool in such apparatus. Typically, in existing reels, drives have been used only while the roll builds on the horizontal, linear rails after several centimeters of web have built up on the reel spool. In order to optimize the structure of the wound web roll, torque must be provided continuously to the reel spool from the beginning of the reeling operation.
In some applications, such as when reeling creped or carbonless copy paper grades, low levels of nip pressure must be provided to prevent damage to the paper product. On conventional Pope-type reels not having center-wind torque, the low nip pressures required to prevent damage to creped and carbonless copy paper does not provide enough friction to drive the web roll being wound.